U.S. patent application number 09/855039 was filed with the patent office on 2001-11-15 for skiving head and process for skiving cylinders and cylinder tubes.
This patent application is currently assigned to ECOROLL AG Werkzeugtechnik. Invention is credited to Ostertag, Alfred.
Application Number | 20010039861 09/855039 |
Document ID | / |
Family ID | 7641957 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010039861 |
Kind Code |
A1 |
Ostertag, Alfred |
November 15, 2001 |
Skiving head and process for skiving cylinders and cylinder
tubes
Abstract
In order to eliminate errors in roundness and the occurrence of
helical waves, a skiving head is provided with at least three
skiving blades arranged in a radially displaceable manner in the
skiving head. With this skiving head, both the requirement for
self-centering of the skiving blade set as well as the requirement
for circular skiving geometry with consistent cutting depth are
fulfilled.
Inventors: |
Ostertag, Alfred; (Celle,
DE) |
Correspondence
Address: |
COLLARD & ROE, P.C.
1077 Northern Boulevard
Roslyn
NY
11576
US
|
Assignee: |
ECOROLL AG Werkzeugtechnik
|
Family ID: |
7641957 |
Appl. No.: |
09/855039 |
Filed: |
May 14, 2001 |
Current U.S.
Class: |
82/1.11 ;
82/53 |
Current CPC
Class: |
Y10T 82/16114 20150115;
B23D 79/04 20130101; Y10T 82/16229 20150115; Y10T 82/10 20150115;
B23D 77/042 20130101; B23B 5/12 20130101; Y10T 407/191
20150115 |
Class at
Publication: |
82/1.11 ;
82/53 |
International
Class: |
B23B 001/00; B23B
005/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 13, 2000 |
DE |
100 23 535.2 |
Claims
What is claimed is:
1. A skiving head for skiving out cylinders, and cylinder tubes,
comprising at least three skiving blades arranged floating in the
skiving head.
2. A skiving head according to claim 1, wherein the skiving head
has a central axis, and wherein adjacent skiving blades are
arranged at similar angular distances to one another in the
direction of the central axis of the skiving head.
3. A skiving head according to claim 1, wherein the skiving head
has a central axis and each skiving blade has at least one cutting
edge, wherein at least three cutting edges of different skiving
blades are arranged rotationally symmetric to the central axis of
the skiving head.
4. A skiving head according to claim 1, wherein all of said skiving
blades are supported by a common conical or pyramidal body movably
arranged in the skiving head, said blades being radially movable in
relation to the skiving head by said body.
5. A skiving head according to claim 4, wherein the conical or
pyramidal body is mounted floating in the skiving head with two
degrees of freedom.
6. A skiving head according to claim 4, further comprising a device
for the changeable determination of a first relative position of
the conical or pyramidal body relative to the skiving blades.
7. A skiving head according to claim 6, further comprising first
spring media for preliminary tensioning of the conical or pyramidal
body into the first relative position.
8. A skiving head according to claim 7, wherein the conical or
pyramidal body is movable against the preliminary tension by the
application of an external force into a second relative
position.
9. A skiving head according to claim 7, further comprising second
spring media for preliminary tensioning of each skiving blade
against the conical or pyramidal body.
10. A skiving head according to claim 9, wherein the second spring
media are arranged so that their direction of effect does not run
through the center of the skiving head.
11. A skiving head according to claim 1, further comprising guides
for guiding the skiving blades, said guides having a ratio of
length to breadth greater than 1.5.
12. A process for the skiving out of a body such as a cylinder or
cylinder tube, comprising: introducing a skiving head into the body
to be peeled out, said skiving head having a central axis and at
least three skiving blades capable of movement radially to the
central axis of the skiving head.
13. A process according to claim 12, wherein each skiving blade
features at least one cutting edge, and wherein the radial distance
between the cutting edges to the central axis of the skiving head
is adjusted via a conical or pyramidal body arranged movable in the
skiving head.
14. A process according to claim 13, wherein the skiving blades are
subjected to preliminary tension against the conical or pyramidal
body.
15. A process according to claim 13, wherein the conical or
pyramidal body is subjected to preliminary tension into a first
operating position relative to the skiving blades.
16. A process according to claim 15, further comprising the step of
pressing the conical or pyramidal body into a second relative
position to displace the skiving head in the peeled-out body
without machining the body by imposing an external force against
the preliminary tension, in which position the radial distance
between the cutting edges and the central axis of the skiving head
is smaller than in the operating position.
17. Bodies comprising cylinders and cylinder tubes, with a
cylindrical cavity, said cavity being machined via a skiving head
having at least three skiving blades floating in the skiving head.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a skiving head and process for
skiving cylinders, cylinder tubes and the like, using a skiving
head. The skiving head has a number of skiving blades arranged
radially and floating in the skiving head.
[0003] 2. The Prior Art
[0004] Such processes and skiving heads are known, for example,
from German Patent Nos. DE 22 23 969 and DE 27 23 622. They serve
in the machining, and in particular the fine machining, of
cylindrical hole walls such as are found in hydraulic cylinders and
cylinder tubes. Such hole walls are fine-machined most economically
by skiving and roller burnishing. Initial materials are generally
drawn precision steel tubes or soft steel tubes with prepared by
boring out, with a small machining allowance of approx. 0.3 to 1 mm
in diameter. These tubes feature straightness errors incurred by
manufacturing, which are not detrimental to the purpose of the
tubes and which therefore do not need to be corrected by the
skiving process.
[0005] However, the surface of the hole wall must be peeled and
roller burnished over the full surface even with cambered
cylinders. Under the given conditions, the skiving blade must
follow the macroform of the tube at almost constant chip depth. To
achieve this, skiving blades arranged in floating fashion have
proved their worth, such as described in DE 27 23 622 or DE 25 18
170 already referred to. The skiving head in this situation is
capable of free radial movement in two planes in relation to the
tool, and the skiving blade(s) is/are in addition capable of radial
movement.
[0006] The known arrangement of the skiving blades guarantees the
self-centering of the blades due to the passive cutting forces of
both cutting edges even when the skiving head is not rotating
centrically due to the effect of outside forces. A disadvantage
with this arrangement, however, is that the skiving blades,
equipped with two mutually-opposed cutting edges, do not
necessarily create a circular hole. Rather, such skiving blades can
carry out a radially floating movement during the rotation of the
skiving head, and in this situation create a hole cross-section
which deviates from the circular. This movement can be incurred due
to an error in roundness already present in the tube, or a slight
disturbance in the balance of force, possibly due to fluctuating
passive cutting force with regular intentional chip breakage, and
may build up and propagate over the entire machining length.
[0007] The hole, measured between two mutually-opposed points, may
indeed feature a constant diameter, but the interior enveloping
circle may be smaller and the outer enveloping circle larger than
the skiving diameter measured in the two-point process. In this
situation "polygons" may be formed, with 3, 5, 7 or more "corners".
These errors in roundness may lead to problems with the assembly of
pistons and seals. The error in roundness frequently runs over the
length of the tube with an angle offset from one tool revolution to
the next, resulting in a helical contour of the cylinder, which as
a rule is regarded as a quality deficiency.
[0008] Tools without floating blades are also known. These include
the reamers such as described in German Patent Nos. DE 19 62 181 B,
DE 16 52 790 A, DE 73 21 746 U, and in U.S. Pat. No. 2,638,020. The
reamer blades are all only capable of adjustment jointly, by the
same dimension in relation to the basic structure of the tool, and
are therefore not installed in a radially floating manner. Reamers
are conceptually designed to produce holes with the smallest
possible errors in straightness. Continuation of machining is
therefore effected in continuation of the previous direction of the
hole bore. If the previous bore was cambered, it is expected of the
reamers that they will eliminate this cambering as much as
possible.
[0009] Cylinder tubes are manufactured from drawn precision steel
tubes with a length of up to 10 meters. Due to the chipless
manufacturing process employed hitherto, these tubes feature errors
in straightness of up to 2 mm/m. At the same time, however, to save
material and money, work is carried out with machining allowances
of less than 1 mm in the diameter. This means that insufficient
machining allowance is provided to make a straight hole out of the
cambered hole. To achieve this with the camber indicated
heretofore, a machining allowance of at least 4 mm in the diameter
would be required. Tools which, like the reamers described earlier,
are designed for the manufacture of the straightest possible holes,
would remove a great deal of material to chips, and in return would
leave other places unmachined. Accordingly, the requirement is
imposed on a skiving head for the skiving of cylinders, cylinder
tubes, and the like, for the skiving tool to follow the macroform
of the hole during machining, and accordingly repeats the existing
errors in straightness. The reamers do not meet this
requirement.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of the invention to provide a
skiving head and process for skiving which will allow for errors in
roundness to be eliminated as far as possible, and to prevent the
occurrence of helical waves.
[0011] This object is accomplished by a skiving head with skiving
blades arranged radially floating in the skiving head, in which at
least three skiving blades are provided for. With such an
arrangement, both the requirement for self-centering of the skiving
blade set as well as circular skiving geometry with constant
cutting depth will be fulfilled.
[0012] In addition to this, the invention has the great advantage
that due to the three skiving blades, the skiving capacity can be
increased in relation to known skiving heads with only two skiving
blades.
[0013] In a preferred embodiment of the invention, in which the
skiving head features a central axis, adjacent skiving blades seen
in the direction of the central axis of the skiving head are
arranged at similar angular distances to one another. This
guarantees the greatest possible centering probability in every
rotation position of the skiving head. The angular distance would
accordingly be 120 degrees with three skiving blades, 90 degrees
with four skiving blades, 72 degrees with five skiving blades, and
60 degrees with six skiving blades. These angles may vary slightly
from sector to sector if appropriate in order to avoid shatter
marks.
[0014] In another preferred embodiment of the invention, in which
the skiving head has a central axis and each skiving blade featured
at least one cutting edge, there are at least three cutting edges
of different skiving blades arranged rotationally symmetrically to
the central axis of the skiving head. For each one cutting edge of
a skiving blade, corresponding cutting edges of up to at least two
other skiving blades are provided for, so that corresponding points
of corresponding cutting edges define a plane which runs
perpendicular to the central axis of the skiving head. Because the
central axis of the skiving head is the main axis of rotation
during the operation of the head, this arrangement likewise has a
positive effect on the centering of the skiving head in the hole
which is to be peeled out.
[0015] The skiving capacity can be further increased by each
skiving blade featuring at least two cutting edges.
[0016] In a particularly advantageous embodiment of the invention,
all skiving blades are supported directly or indirectly by a common
conical or pyramidal body arranged in a displaceable manner in the
skiving head, and can be displaced via this body radially to the
skiving head. In this situation, depending on the design of the
skiving head, the body may also take the form of a cone or
truncated cone as well as of a pyramid or truncated pyramid. The
term pyramid is not restricted here in the conventional sense to
such regular polyhedra as have a square base and four congruent
isosceles triangles as side surfaces, but is to be understood in
the meaning of the geometric definition, and in particular may have
a base with as many sides as skiving blades are provided.
[0017] Both a conical and pyramidal body allow, by simple
displacement of the body alone the central axis of the skiving
head, for the skiving blades to be pressed radially outwards. In
this way, the corresponding skiving diameter can be adjusted in a
particularly simple manner.
[0018] In this situation, the conical or pyramidal body is
preferably arranged floating in the skiving head. There is a means
for the changeable determination of a first relative position of
the conical or pyramidal body relative to the skiving blades, so
that the conical or pyramidal body can be subjected to preliminary
tension by appropriate spring media into the first relative
position. This first relative position is as a rule the operating
position of the skiving head, in which the skiving blades are
therefore adjusted to the desired skiving diameter.
[0019] In order to be able to withdraw the skiving head from the
peeled-out body easily and without the occurrence of markings, the
conical or pyramidal body can be designed so that it is capable of
being moved against the preliminary tension by the use of an outer
force, and a hydraulic force in particular, into a second relative
position relative to the skiving blades. This second relative
position corresponds to the withdrawn position of the skiving
blades, so that this is accordingly no longer located close to the
surface to be peeled out and the skiving head is capable of being
moved and positioned in the body which is to be peeled out.
[0020] In order to guarantee that the skiving blades are always in
contact, directly or indirectly, in the conical or pyramidal body,
and therefore, by changing the relative position of conical or
pyramidal body and skiving blades, follow the desired setting of
the skiving diameter, there are spring media which subject the
skiving blades to preliminary tension against the conical or
pyramidal body. These second spring media are arranged so that
their direction of effect does not run through the center of the
tool.
[0021] To prevent the tilting of the skiving blades, they are
guided in guides, of which the length to breadth ratio is greater
than 1.5, and preferably greater than 2. The ratio of length to
breadth may even reach 4 or 5 in order to achieve good guidance
effect. In this context, the term length means the extension of the
guide in the radial direction, while the term breadth means the
extension of the guide in the axial direction.
[0022] The invention also comprises a process for skiving out a
cylinder, cylinder tube, or the like by means of a skiving head
introduced into the body which is to be peeled out with a central
axis and a number of skiving blades. The skiving head has at least
three skiving blades radially movable relative to the central axis
of the skiving head.
[0023] In a preferred embodiment of the process, whereby each
skiving blade features at least one cutting edge, the radial
distance between the cutting edges and the central axis of the
skiving head, and therefore the skiving diameter, is adjusted via a
conical or pyramidal body arranged so as to be capable of movement
in the skiving head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Other objects and features of the present invention will
become apparent from the following detailed description considered
in connection with the accompanying drawings. It is to be
understood, however, that the drawings are designed as an
illustration only and not as a definition of the limits of the
invention.
[0025] In the drawings, wherein similar reference characters denote
similar elements throughout the several views:
[0026] FIG. 1 shows a skiving head according to the invention in a
partially sectional side view along the central axis;
[0027] FIG. 1a is a detailed view of the skiving head shown in FIG.
1, in the area of the blades;
[0028] FIG. 2 is a partially sectional view of the skiving head
according to FIG. 1, seen in the direction of the central axis;
[0029] FIG. 3 illustrates the effect of the centering forces during
the operation of the skiving head; and
[0030] FIG. 4 shows an alternative embodiment of a skiving head in
a partial sectional side view along the central axis.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] Referring now in detail to the drawings, FIGS. 1 to 3 show a
skiving head designated in its entirety by 9, in which a total of
three skiving blades 10 are arranged in a radially displaceable
manner in a cylindrical housing 11.
[0032] Each skiving blade 10 has two cutting edges 3 and 3'.
Skiving blades 10 are guided in guides 10' with large
length-to-breadth ratios, which prevent the tilting of the skiving
blades. In the embodiment shown, this guide is more than three
times longer than wide, and to be precise even more than five
times. There are guides 25 that are always arranged between the
skiving blades.
[0033] As indicated in FIG. 2 with only one blade, each skiving
blade 10 is pressed by spring media, in this case in the form of
pressure spring elements 13, radially inwards against a conical
body which adjusts the skiving diameter. The conical body is in the
form of a truncated cone 12. For this purpose each skiving blade 10
features a mounting 13' for one pressure spring element 13 in each
case. Each skiving blade 10 is subjected to preliminary tension by
a pressure spring element 13 in the direction onto the cone, as
indicated by the arrows 13" in FIGS. 2 and 3, of which only a few
have been provided with reference indicators for the sake of easier
overview. Truncated cone 12 is thereby stored swimmingly in the
skiving head with the degrees of freedom 12' and 12"
[0034] Pressure spring elements 13, during the skiving process and
in the introduced state, in which the skiving blades are located in
a withdrawn position seen in a radial direction towards the central
axis, provide for sustained contact of the blades 10 with the
truncated cone 12.
[0035] To determine a first relative position of the truncated cone
12 and skiving blades 10, a screw-spacer element combination 15 is
provided for. Spring media, in this case in the form of a coil
spring 14, tension the truncated cone into this relative position,
which corresponds to the operating position in which the tool is
ready to carry out skiving.
[0036] By the application of a force in the direction of arrow 16,
for example by means of an inherently known hydraulic system, not
shown here in any greater detail, the truncated cone 12 can be
displaced along the common central axis 16' of skiving head 9 and
truncated cone 12 against the preliminary tension of the spring 14,
as a result of which the skiving blades 10 move radially inwards
into a withdrawn position.
[0037] Truncated cone 12 is arranged floating in skiving head 9. As
shown in FIG. 3, an error in straightness of a cylinder tube which
is to be peeled out by the dimension 19 means a change in the hole
contour 17 and the hole axis 17a by the dimension 19 into the
position 18 or 18a respectively. This leads to an increase in the
passive cutting forces of all the cutting edges operating in the
drawing above the center, and at the same time to a decrease in the
lower positions in the drawing. The truncated cone 12 reacts to
this with a radial downwards movement 20 by the dimension 19. In
this way, the entire blade set centers itself, while maintaining
the envelope geometry onto the new tube center. Accordingly, the
requirements for the self centering of the skiving blade set,
circular skiving geometry, and consistent cutting depth are
fulfilled. The compensation movement is effected under the rotation
of the skiving tool or continuously with the tool at a standstill
and with the tool rotating, and can be carried out in any desired
direction depending on the tube camber.
[0038] FIG. 4 shows an embodiment in which the force 16" engages on
the broad side of the truncated cone 12"' and the coil spring 14'
engages via the screw-spacer combination 15' on the smaller
diameter of the truncated cone 12"'. This arrangement also incurs a
displacement of the cutting edges 3" and the skiving blade 10"
relative to the housing 11'.
[0039] Numerous divergences and further embodiments are possible
within the framework of the concept of the invention, which relate,
for example, to the number and arrangement of the skiving blades
and cutting edges. It is possible, for example, for skiving out
large diameters, to use skiving heads which feature more than the
three skiving blades described above. Central to the invention in
any event is the fact that there are more than two skiving blades,
which clearly reduces the probability of occurrence of
unintentional radial oscillation.
[0040] Accordingly, while only a few embodiments of the present
invention have been shown and described, it is obvious that many
changes and modifications may be made thereunto without departing
from the spirit and scope of the invention.
* * * * *